Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $234.25   4.286%   $244.29   $244.29   $244.30   $244.30  
  Purchase #2 $238.88   3.244%   $246.6293   $246.63   $246.65   $246.60  
  Purchase #3 $26.92   6.628%   $28.7043   $28.70   $28.70   $28.70  
  Purchase #4 $245.41   6.590%   $261.5825   $261.58   $261.60   $261.60  
  Purchase #5 $145.67   11.560%   $162.5095   $162.51   $162.50   $162.50  
  Purchase #6 $173.38   4.563%   $181.2913   $181.29   $181.30   $181.30  
  Purchase #7 $55.95   5.769%   $59.1778   $59.18   $59.20   $59.20  
  7 purchase totals = $1,120.46       $1,184.1847   $1,184.18   $1,184.25   $1,184.20